 // 二叉树逐层遍历 https://leetcode.cn/problems/binary-tree-level-order-traversal/

#include <vector>
#include <queue>
#include <sstream>
#include <iostream>
using namespace std;

struct TreeNode {
    int val;
    TreeNode *left;
    TreeNode *right;
    TreeNode() : val(0), left(nullptr), right(nullptr) {}
    TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
    TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
};


class Solution {
public:
    vector<vector<int>> levelOrder(TreeNode* root) {
        // 记录最终结果
        vector<vector<int>> ret; 
        if(root == nullptr) return ret;
        queue<TreeNode*> que;
        que.push(root);

        while(!que.empty()){
            // 记录一层的结果
            vector<int> line;
            // 关键：记录一层的节点个数，区分层数 
            int sz = que.size();
            for (int i = 0; i < sz; i++){
                TreeNode* cur = que.front();
                que.pop();
                line.push_back(cur->val);
                if(cur->left != nullptr){
                    que.push(cur->left);
                }
                if(cur->right != nullptr){
                    que.push(cur->right);
                }
            }
            ret.push_back(line);
        }
        return ret;
    }
};

void trimLeftTrailingSpaces(string &input) {
    input.erase(input.begin(), find_if(input.begin(), input.end(), [](int ch) {
        return !isspace(ch);
    }));
}

void trimRightTrailingSpaces(string &input) {
    input.erase(find_if(input.rbegin(), input.rend(), [](int ch) {
        return !isspace(ch);
    }).base(), input.end());
}

TreeNode* stringToTreeNode(string input) {
    trimLeftTrailingSpaces(input);
    trimRightTrailingSpaces(input);
    input = input.substr(1, input.length() - 2);
    if (!input.size()) {
        return nullptr;
    }

    string item;
    stringstream ss;
    ss.str(input);

    getline(ss, item, ',');
    TreeNode* root = new TreeNode(stoi(item));
    queue<TreeNode*> nodeQueue;
    nodeQueue.push(root);

    while (true) {
        TreeNode* node = nodeQueue.front();
        nodeQueue.pop();

        if (!getline(ss, item, ',')) {
            break;
        }

        trimLeftTrailingSpaces(item);
        if (item != "null") {
            int leftNumber = stoi(item);
            node->left = new TreeNode(leftNumber);
            nodeQueue.push(node->left);
        }

        if (!getline(ss, item, ',')) {
            break;
        }

        trimLeftTrailingSpaces(item);
        if (item != "null") {
            int rightNumber = stoi(item);
            node->right = new TreeNode(rightNumber);
            nodeQueue.push(node->right);
        }
    }
    return root;
}

int stringToInteger(string input) {
    return stoi(input);
}

string treeNodeToString(TreeNode* root) {
    if (root == nullptr) {
      return "[]";
    }

    string output = "";
    queue<TreeNode*> q;
    q.push(root);
    while(!q.empty()) {
        TreeNode* node = q.front();
        q.pop();

        if (node == nullptr) {
          output += "null, ";
          continue;
        }

        output += to_string(node->val) + ", ";
        q.push(node->left);
        q.push(node->right);
    }
    return "[" + output.substr(0, output.length() - 2) + "]";
}

int main() {
    string line;
    while (getline(cin, line)) {
        TreeNode* root = stringToTreeNode(line);
        
        vector<vector<int>> ret = Solution().levelOrder(root);

        for(auto line : ret){
            for(auto ele : line){
                cout<<ele<<" ";
            }
            cout<<endl;
        }
    }
    return 0;
}